Imagine you can apply three different forces F1=40 N, F2=50 N and F3=60 N to a body. The forces' magnitudes are fixed, but you can apply them in any directions in the x-y plane.
A. Make a sketch to show how you'd apply these forces to achieve the largest possible resultant force.
B. Make a sketch to show one way to apply these forces to get a 70-N resultant force, pointing in the +X direction.
C. Make a sketch proving that three forces with these magnitudes can add to give zero net force.